Interpretive Summary: Information on integrated weed management (IWM) systems is needed so growers can adopt effective long-term jointed goatgrass control strategies to reduce chemical inputs, enhance winter wheat yields and grain quality, and improve farm profitability and sustainability. Jointed goatgrass is a winter annual grass weed that has similar ancestry to winter wheat, infests almost 5 million acres of wheat in the Pacific Northwest, Intermountain, and Great Plains regions of the United States, and costs growers approximately $150 million annually to control. In the past, jointed goatgrass research has focused on single component management strategies. In 1995, a long-term, three-state IWM field study was initiated to evaluate and identify effective IWM systems for jointed goatgrass management. The systems evaluated included combinations of either one-time stubble burn or no burn, a rotation of either one or three years out of winter wheat production, and either a standard or an integrated practice of planting winter wheat. At Washington and Oregon in heavy stubble residue and moderate to heavy weed infestations, two effective IWM systems were identified. The two systems, a one-time burn, three years out of winter wheat, and either the standard or integrated practices of planting winter wheat consistently had the highest grain yield, best grain quality (reduced weed seed contamination) and lowest weed densities. Adoption of these IWM systems by wheat growers would reduce jointed goatgrass competition and infestations, decrease farm chemical inputs, and improve farm profitability, sustainability and environmental quality.

Technical Abstract:
Jointed goatgrass is an invasive winter annual grass weed that is a particular problem in the low- to intermediate-rainfall zones of the Pacific Northwest (PNW). For the most part, single-component research has been the focus of previous jointed goatgrass studies. In 1996, an integrated field systems study for the management of jointed goatgrass was initiated in Washington (WA), Idaho (ID), and Oregon (OR) in the traditional winter wheat (WW)–fallow (F) region of the PNW. The study evaluated eight integrated weed management (IWM) systems that included combinations of either a one-time stubble burn (Y) or no-burn (N), a rotation of either WW-F-WW or spring wheat (SW)-F-WW, and either a standard practice (S) or an integrated practice (I) of planting WW. This study was the first to evaluate and identify complete IWM systems for jointed goatgrass control, unlike previous component studies designed to evaluate and analyze individual factors. At ID, in a very low weed density, no IWM system was identified that consistently yielded highest, reduced grain dockage, and reduced weed densities. At WA, in a moderate population of jointed goatgrass, the best IWM system based on the above responses was the Y-SW-F-WW-S system. At WA, this system was better than the I planting system because the competitive WW variety did not perform well in drought conditions the second year of WW. At OR, a location with a high weed density, the IWM system Y-SW-F-WW-I produced consistently higher grain yields, reduced grain dockage, and reduced jointed goatgrass densities. Adoption of these IWM systems by PNW wheat growers would increase farm profits, decrease farm inputs, reduce herbicide resistance in jointed goatgrass and improve environmental quality.